BEIRUT, Oct 19 (Reuters) - Senior Lebanese intelligence official Wissam al-Hassan, who led the investigation that implicated Syria and Hezbollah in the killing of former prime minister Rafik al-Hariri, was killed in the Beirut explosion on Friday, a Lebanese official said.

"I can just say that it is true, he is dead," the official, who worked with al-Hassan, told Reuters.

Al-Hassan was also the brain behind uncovering a recent bomb plot that led to the arrest of a Lebanese politician allied to President Bashar al-Assad.

Al-Hassan was no ordinary officer. He was a close aide to Hariri, a Sunni Muslim who was killed in a 2005 bomb attack.

He led the Hariri investigation and uncovered evidence that implicated Syria and Lebanon's pro-Iranian Shi'ite Muslim group in the killing.

Hariri supporters accused Syria and then Hezbollah of killing him - a charge they both deny. An international tribunal accused several Hezbollah members of involvement in the murder.

Lebanese rescue workers and civilians carry an injured man, from the scene of an explosion in the mostly Christian neighborhood of Achrafiyeh, Beirut, Lebanon, Friday Oct. 19, 2012. Lebanese Red Cross and security officials say a car bomb in east Beirut has killed at least eight people and wounded dozens in the worst blast the city has seen in years, coming at a time when Lebanon has seen a rise in tension and eruptions of clashes stemming from the civil war in neighboring Syria. (AP Photo/Hussein Malla)